Linux Fedora Memory Management - Hasan H. BALIK · 2017-04-11 · in Linux fedora when the amount...
Transcript of Linux Fedora Memory Management - Hasan H. BALIK · 2017-04-11 · in Linux fedora when the amount...
Linux Fedora Memory
Management
Submitted by:KHALID ABDULWAHID KADHIM ST.NO(163103073)
Submitted ToProf .Dr. Hassan Huseyin Balik
Outline
1.0 Introduction( Fedora , Memory Management ).
1.1 memory management techniques used by Fedora.
1.2 Garbage collection( Pruning, Trashing, Deleting ).
1.3 Swapping.
1.4 Virtual memory (Advantages , Disadvantages ).
1.5 Conclusion.
1.0 Introduction
What is FedoraFedora is an open source operating system built
on the Linux kernel.
The first release of Fedora was on 16th
November 2003 as Fedora Core 1.
Fedora is developed by a community of
developers collectively known as the Fedora
Project.
1.0 Memory Management :
A good memory management system must carry
out the following tasks:
• Allocation of memory space blocks for
different tasks
• Allow sharing of memory
• Memory space which is being used should
be protected. This is required to prevent a
user from changing a task carried out by
another user.
• Optimization of available memory
1.1 Memory management techniques used by Fedora:
Garbage collection
Swapping
Virtual Memory
Memory hierarchy
Overcommit accounting
Out Of Memory (OOM)
Drop caches
1.2 Garbage collection
Garbage collection is a form of automatedmemory management technique in whichthe operating system removes objects, dataor other regions of the memory which areno longer in use by the system or theprogram.
In Fedora, garbage collection is primarily broken down to three stages, they are:
Pruning
Trashing
Deleting
Pruning
In this stage, the operating system identifies
unwanted objects, builds or data and they
are detached from certain tags according to
garbage collection policies set by Fedora.
These policies allow rules based on tag,
signature and package.
Trashing
This is the stage in which, the system overlooks the objects,
builds or data which was untagged in pruning stage. After
this, these objects, builds or data are tagged with a trashcan tag
which instructs the system to send these builds for deletion.
The garbage collector sends a certain objects, builds or data for
deletion only if it meets the following requirement
1. The objects, builds or data is untagged for at least 5 days
2. There are not protection key signed on the objects, builds or
data
Deleting
This is the final stage in garbage collection, in
this stage, all the objects, builds or data are
examined for the last time for any mistakes in
their tags. The objects, builds or data is usually
deleted after it has been tagged with the trashcan
tag for more than the grace period (4 weeks by
default).
1.3 Swapping :
in Linux fedora when the amount of physical memory
(RAM) is full .if the system needs more memory and ram is
full ,inactive ,blocks or timeouts process are swapped
temporarily out of main memory to secondary storage
(disk) and make that memory available to other processes.
At some later time, the system swaps back the process
from the secondary storage to main memory.
1.4 Virtual Memory• Virtual memory is implemented in Fedora since it is a
multitasking and multiuser operating system. These features
require necessary protection and ability to execute different
process simultaneously whose cumulated process size can
be greater than the primary memory available in the system.
• Virtual memory basically extends the users primary memory
by considering the hard disk as if it were an additional RAM
• Virtual memory allows the computer to look at areas of RAM
which have not been used for a while and copies those areas
onto the hard disk.
Advantages of Virtual Memory• Virtual memory allows the system to function as if it has
more RAM than it actually does.
• A program or process can run on a system even though there
isn’t enough primary memory required for the program or
process to run.
• Since hard disk space is much cheaper than RAM space,
users need not spend a lot of money upgrading their RAM.
Disadvantages of Virtual Memory
There will be a significant loss of system performanceif the system relies too much on the virtual memory.
The implementation of virtual memory requiresallocation of certain portion of hard disk space for itsuse.
The system might be unstable because of the constantswap of information between hard disk and RAM.
1.5 Conclusion
• Memory management is a crucial section
of any operating system. This is because a
poor memory management can result in
failure of operating system. If the operating
system did not implement appropriate
memory management technique, this
result in crashed constantly.
Resources
Madnick, Stuart; Donovan, John (1974). Operating
Systems. McGraw-Hill Book Company. ISBN 0-07-039455-
5.
Green, Paul. "Multics Virtual Memory - Tutorial and
Reflections". Retrieved May 9, 2012.
https://linux-mm.org
https://docs.fedoraproject.org/en-
US/Fedora/16/html/Resource_Management_Guide/sec-
memory.html
https://www.ukessays.com/essays/information-
technology/the-memory-management-of-operating-
systems-information-technology-essay.php
Thank you